Padeliporfin is a vascular-acting photosensitizer consisting of a water-soluble, palladium-substituted bacteriochlorophyll derivative with antineoplastic activity. After administration, the drug is activated locally when the tumor bed is exposed to low-power laser light; reactive oxygen species (ROS) are formed upon activation and ROS-mediated necrosis may occur at the site of interaction between the photosensitizer, light and oxygen. Padeliporfin is approved in Europe for the treatment of adult patients with previously untreated, unilateral, low-risk, adenocarcinoma of the prostate and is marketed under tradename TOOKAD.

Padoporfin (palladium bacteriopheophorbide, also known as WST-09) from the bacteriopheophorbide family was used as a photosensitizer in clinical trials for prostate and kidney cancers. Padoporfin successfully completed phase III clinical trial where was shown its efficacy and safety for localized prostate cancer. Padoporfin is a powerful photosensitizer that produces photodynamic therapy effects similar to those seen with longer acting drugs, but with the major advantages of a short drug-light interval and rapid clearance.

Temoporfin is a photosensitizer (based on chlorin) used in photodynamic therapy for the treatment of squamous cell carcinoma of the head and neck. It is marketed in the European Union under the brand name Foscan. It is used in patients in whom other treatments have stopped working, and who are not suitable for radiotherapy (treatment with radiation), surgery or systemic chemotherapy (medicines used to treat cancer; ‘systemic’ means that they are given as treatments throughout the body). When Foscan is injected, temoporfin is distributed within the body, including within the tumour. When it is illuminated with laser light of a specific wavelength, temoporfin is activated and reacts with oxygen in the cells to create a highly reactive and toxic type of oxygen. This kills the cells by reacting with and destroying their components, such as their proteins and DNA. By restricting the illumination to the tumour, cell damage is limited to the tumour cells, leaving other areas of the body unaffected. The U.S. Food and Drug Administration (FDA) declined to approve Foscan in 2000. The EU approved its use in June 2001.

Verteporfin (trade name Visudyne), a benzoporphyrin derivative, is a medication used for the treatment of patients with predominantly classic subfoveal choroidal neovascularization due to age-related macular degeneration, pathologic myopia or presumed ocular histoplasmosis syndrome. Verteporfin can also be used to destroy tumors. Verteporfin is a 1:1 mixture of two regioisomers (I and II), VISUDYNE therapy is a two-stage process requiring administration of both verteporfin for injection and nonthermal red light. Verteporfin accumulates in these abnormal blood vessels and, when stimulated by nonthermal red light with a wavelength of 689 nm in the presence of oxygen, produces highly reactive short-lived singlet oxygen and other reactive oxygen radicals, resulting in local damage to the endothelium and blockage of the vessels. Verteporfin is also used off-label for the treatment of central serous retinopathy. Verteporfin is given intravenously, 15 minutes before laser treatment. Light activation of verteporfin results in local damage to neovascular endothelium, resulting in vessel occlusion. Damaged endothelium is known to release procoagulant and vasoactive factors through the lipo-oxygenase (leukotriene) and cyclo-oxygenase (eicosanoids such as thromboxane) pathways, resulting in platelet aggregation, fibrin clot formation and vasoconstriction. Verteporfin appears to somewhat preferentially accumulate in neovasculature, including choroidal neovasculature. However, animal models indicate that the drug is also present in the retina. Therefore, there may be collateral damage to retinal structures following photoactivation including the retinal pigmented epithelium and outer nuclear layer of the retina. The temporary occlusion of choroidal neovascularization (CNV) following VISUDYNE therapy has been confirmed in humans by fluorescein angiography.

Porfimer is a photosensitizing agent used in the photodynamic therapy (PDT) of tumors. Porfimer sodium was approved under the brand name PHOTOFRIN for the palliation of patients with completely obstructing esophageal cancer, or of patients with partially obstructing esophageal cancer who, in the opinion of their physician, cannot be satisfactorily treated with Nd:YAG laser therapy. For the reduction of obstruction and palliation of symptoms in patients with completely or partially obstructing endobronchial nonsmall cell lung cancer (NSCLC). For the treatment of microinvasive endobronchial NSCLC in patients for whom surgery and radiotherapy are not indicated. In addition, for the ablation of high-grade dysplasia in Barrett’s esophagus patients who do not undergo esophagectomy. The cytotoxic and antitumor actions of PHOTOFRIN® are light and oxygen dependent. Photodynamic therapy with Porfimer sodium is a two-stage process. The first stage is the intravenous injection of the drug, which mainly is concentrated in the tumor tissues for a longer period. Illumination with 630 nm wavelength laser light constitutes the second stage of therapy. Cellular damage is a consequence of the propagation of radical reactions. Radical initiation may occur after porfimer absorbs light to form a porphyrin excited state. Tumor death also occurs through ischemic necrosis secondary to vascular occlusion that appears to be partly mediated by thromboxane A2 release. The laser treatment induces a photochemical, not a thermal, effect. The necrotic reaction and associated inflammatory responses may evolve over several days.

Verteporfin (trade name Visudyne), a benzoporphyrin derivative, is a medication used for the treatment of patients with predominantly classic subfoveal choroidal neovascularization due to age-related macular degeneration, pathologic myopia or presumed ocular histoplasmosis syndrome. Verteporfin can also be used to destroy tumors. Verteporfin is a 1:1 mixture of two regioisomers (I and II), VISUDYNE therapy is a two-stage process requiring administration of both verteporfin for injection and nonthermal red light. Verteporfin accumulates in these abnormal blood vessels and, when stimulated by nonthermal red light with a wavelength of 689 nm in the presence of oxygen, produces highly reactive short-lived singlet oxygen and other reactive oxygen radicals, resulting in local damage to the endothelium and blockage of the vessels. Verteporfin is also used off-label for the treatment of central serous retinopathy. Verteporfin is given intravenously, 15 minutes before laser treatment. Light activation of verteporfin results in local damage to neovascular endothelium, resulting in vessel occlusion. Damaged endothelium is known to release procoagulant and vasoactive factors through the lipo-oxygenase (leukotriene) and cyclo-oxygenase (eicosanoids such as thromboxane) pathways, resulting in platelet aggregation, fibrin clot formation and vasoconstriction. Verteporfin appears to somewhat preferentially accumulate in neovasculature, including choroidal neovasculature. However, animal models indicate that the drug is also present in the retina. Therefore, there may be collateral damage to retinal structures following photoactivation including the retinal pigmented epithelium and outer nuclear layer of the retina. The temporary occlusion of choroidal neovascularization (CNV) following VISUDYNE therapy has been confirmed in humans by fluorescein angiography.

Aminolevulinic Acid is the first compound in the porphyrin synthesis pathway. The metabolism of aminolevulinic acid (ALA) is the first step in the biochemical pathway resulting in heme synthesis. Aminolevulinic acid is not a photosensitizer, but rather a metabolic precursor of protoporphyrin IX (PpIX), which is a photosensitizer. The synthesis of ALA is normally tightly controlled by feedback inhibition of the enzyme, ALA synthetase, presumably by intracellular heme levels. ALA, when provided to the cell, bypasses this control point and results in the accumulation of PpIX, which is converted into heme by ferrochelatase through the addition of iron to the PpIX nucleus. Marketed under the brand name LEVULAN KERASTICK for Topical Solution plus blue light illumination using the BLU-U Blue Light Photodynamic Therapy Illuminator, it is indicated for the treatment of minimally to moderately thick actinic keratoses (Grade 1 or 2, see table 2 for definition) of the face or scalp. Aminolevulinic acid is also being studied in the treatment of other conditions and types of cancer. An orally-administered in vivo diagnostic agent, Aminolevulinic acid, is used in photodynamic diagnosis (PDD) whose aim is to help doctors visualize the tumor tissue during surgical resection of malignant glioma, it is already sold in over 20 European countries including Germany and the U.K. According to the presumed mechanism of action, photosensitization following application of aminolevulinic acid (ALA) topical solution occurs through the metabolic conversion of ALA to protoporphyrin IX (PpIX), which accumulates in the skin to which aminolevulinic acid has been applied. When exposed to light of appropriate wavelength and energy, the accumulated PpIX produces a photodynamic reaction, a cytotoxic process dependent upon the simultaneous presence of light and oxygen. The absorption of light results in an excited state of the porphyrin molecule, and subsequent spin transfer from PpIX to molecular oxygen generates singlet oxygen, which can further react to form superoxide and hydroxyl radicals. Photosensitization of actinic (solar) keratosis lesions using aminolevulinic acid, plus illumination with the BLU-UTM Blue Light Photodynamic Therapy Illuminator (BLU-U), is the basis for aminolevulinic acid photodynamic therapy (PDT).

Hemin (trade name Panhematin) is a protoporphyrin IX containing a ferric iron ion (heme B) with a chloride ligand, which is is indicated for the amelioration of recurrent attacks of acute intermittent porphyria temporally related to the menstrual cycle in susceptible women. Manifestations such as pain, hypertension, tachycardia, abnormal mental status and mild to progressive neurologic signs may be controlled in selected patients with this disorder. the therapy for the acute porphyrias is not curative. Heme acts to limit the hepatic and/or marrow synthesis of porphyrin. This action is likely due to the inhibition of δ-aminolevulinic acid synthetase, the enzyme which limits the rate of the porphyrin/heme biosynthetic pathway. The exact mechanism by which hematin produces symptomatic improvement in patients with acute episodes of the hepatic porphyrias has not been elucidated.

Motexafin lutetium is pentadentate aromatic metallotexaphyrin with photosensitizing properties patented by Pharmacyclics, Inc. as anticancer agent that enhances the cytotoxic potential of photodynamic therapy through several mechanisms, including depleting intracellular reducing metabolites that are necessary for repairing the oxidative damage induced by irradiation. Motexafin lutetium catalyzes the oxidation of intracellular reducing metabolites such as ascorbate, glutathione, nicotinamide adenine dinucleotide phosphate, and protein thiols, generating reactive oxygen species in a process known as futile redox cycling. The depletion (through oxidation) of these reducing metabolites removes the substrate necessary in a cell to repair oxidative damage induced by photodynamic therapy and, left unrepaired, such oxidative DNA damage is converted into lethal double-stranded breaks. Motexafin lutetium has the potential to combine the features of selective localization, ability to be activated by deeply penetrating far-red light, low incidence of skin photosensitization and water solubility. The product was in clinical development as a treatment for several types of solid tumors (as Lutrin), age-related macular degeneration (as Optrin), atherosclerosis and prevention of restenosis (as Antrin).

Methyl aminolevulinate is a prodrug that is metabolised to Protoporphyrin IX (a photosensitizer) used in photodynamic therapy. Photosensitization following application of methyl aminolevulinate cream occurs through the metabolic conversion of methyl aminolevulinate (prodrug) to photoactive porphyrins (PAP), which accumulates in the skin lesions to which the cream has been applied. When exposed to light of appropriate wavelength and energy, the accumulated photoactive porphyrins produce a photodynamic reaction, resulting in a cytotoxic process dependent upon the simultaneous presence of oxygen. The absorption of light results in an excited state of porphyrin molecules, and subsequent spin transfer from photoactive porphyrins to molecular oxygen generates singlet oxygen, which can further react to form superoxide and hydroxyl radicals. Methyl aminolevulinate is used for topical use, in combination with 570 to 670 nm wavelength red light illumination, in the treatment of non-hyperkeratotic actinic keratoses of the face and scalp in immunocompetent patients when used in conjunction with lesion preparation (debridement using a sharp dermal curette).